Pressure spray type fuel injection nozzle having air discharge openings

ABSTRACT

A fuel injection nozzle of the type which injects fuel from a nozzle opening with pressure in the form of a conical spray of fuel particles, in which air discharge openings are provided around the nozzle opening. The air discharge openings each have an angle of inclination and an angle of torsion to the axis of the nozzle opening and cause a spiral flow of air which contacts from the outside the outer periphery of the conical spray of fuel particles injected into a combustion chamber and thereby divides coarse fuel particles at the outer periphery of the conical spray into smaller particles. These air discharge openings are communicated with a flow passage of combustion air inside a combustion element.

United States Patent [191 Sato et al.

[ Aug. 27, 1974 Inventors: Isao Sato; Tadahisa Masai, both of Hitachi,Japan Assignee: Hitachi, Ltd., Tokyo, Japan Filed: Feb. 23, 1973 Appl.No.: 335,312

U.S. Cl 239/406, 431/352 Int. Cl. F23d 15/00 Field of Search 239/400,403, 405, 406,

[56] References Cited 12/1971 Hopkins 239/406 UX 2/1972 Dimick 239/406 X3,713,588 1/1973 Sharpe 239/406 X Primary ExaminerM. Henson Wood, Jr.Assistant Examiner-Michael Y. Mar

Attorney, Agent, or FirmCraig and Antonelli [5 7 ABSTRACT A fuelinjection nozzle of the type which injects fuel from a nozzle openingwith pressure in the form of a conical spray of fuel particles, in whichair discharge openings are provided around the nozzle opening. The airdischarge openings each have an angle of inclination and an angle oftorsion to the axis of the nozzle opening and cause a spiral flow of airwhich contacts from the outside the outer periphery of the conical sprayof fuel particles injected into a combustion chamber and thereby dividescoarse fuel particles at the outer periphery of the conical spray intosmaller particles. These air discharge openings are communicated with aflow passage of combustion air inside a combustion element.

6 Claims, 7 Drawing Figures JIIIII 1111/11/11 IIIIIIIIIIII IIIIIII/[IYTIPAIENIEBAUBZYW 3.831.854

SHCEI 10$ 2 PAIEIIIEIIIIIIN H 3.831.854

85m E W 2 (T F I G. 5

E 9 I I DUAL OPENING TYPE, sPIRAL FUEL NOZZLE j a l.0 Q o O FUEL NOZZLE5 o 0 0 [OF THE INVENTION LU I- EE E; (5% 5m 0 Ms OF 0 O FU L NOZZLE 2OO|00 0 I00 200 (mm) RADIAL DISTANCE FROM THE CENTER OF FUEL NOZZLE 4wDUAL OPENING TYPE A I SPIRAL FUEL NOZZLE f N o o I FUEL NOZZLE a I OFTHE INVENTION 5200- o M i o o [I o E IOO- T i O E [AXIS OF FUEL NOZZLE3E -2oo -IO0 6 I60 260 (mm) RADIAL DISTANCE FROM THE CENTER OF FUELNOZZLE lzzwi ,I i I PRESSURE SPRAY TYPE FUEL INJECTION NOZZLE HAVING AIRDISCHARGE OPENINGS BACKGROUND OF THE INVENTION This invention relates toa pressure spray type fuel injection nozzle used with gas turbines.

Combustion elements used in gas turbines and boilers are becoming largerand larger in capacity to meet economical demands. On the other hand,fuels used in such combustion elements are changing from more volatileoils, such as kerosine and light oil, to less volatile oils, such asheavy oil, containing a large amount of residual oil, in considerationof effective use of the petroleum resources. These tendencies areaggravating air pollution by the unburned hydrocarbons, carbon monoxide,nitrogen oxides, smoke and dusts contained in the exhaust gases from thecombustion elements. In this view, removal of the air pollutingsubstances contained in the exhaust gases is an important problem inincreasing the capacity of the combustion elements and in using lessvolatile oils, and countermeasures are required.

The combustion element of gas turbine, as compared with that of boiler,is extremely narrower in the size of .combustion chamber and is usedunder severer operational conditions, such as quick starting andstopping. Therefore, even if light oil is used as fuel, carbon containedin the fuel is separated in the combustion chamher and the separatedcarbon is released directly into the atmosphere, which imparts asufficiently visible black color to the exhaust gas. For the gasturbines which are considered as discharging less amounts of airpolluting substances than other heat engines, the suppression of smokegeneration is an important problem.

For the suppression of smoke generation, there are known two methods.Namely, one is an indirect method in which a desmoking agent is added tofuel and the other one is a direct method in which the construction ofthe combustion element is designed best to suppress the generation ofsmoke. In the former method, manganese and manganese compounds arechiefly used as the desmoking agents. However, since the desmoking agentmust be mixed in fuel beforehand, this method has some defects, such asthat mixing means is required for mixing the desmoking agent with fuel,that the desmoking agent cannot be mixed uniformly in the fuel, and thatthe secondary products of the desmoking agent resulting from thecombustion are discharged into the atmosphere, causing secondary airpollution, and is rarely being used at the present time.

The generation of smoke, as is well known, is attributable to thepresence of local excess fuel regions in the primary combustion regionwithin the combustion chamber, and therefore, can be prevented byeliminating such local excess fuel regions. In order to eliminatedirectly the source of smoke generation, it is only necessary toencourage mixing of air and fuel and thereby to promote completecombustion of fuel and prevent separation of carbon. As a method, therecan be considered to increase the area of a primary air supply openingof the combustion element. This method aims to encourage fuel-air mixingby supplying a large amount of primary air and thereby to eliminate theexcess fuel regions. However, the generation of smoke cannot beprevented, simply by supplying the primary air in a large amount, andthis is the very fact which makes the subject of combustion complicatedand difficult to deal with. In case of a liquid fuel, the evaporationstage of the liquid fuel droplets is important and the diameter of thedroplets has a significant influence on the combustion of fuel. It iswell known that the evaporation time of a liquid droplet is proportionalto the square of the diameter thereof. Therefore, it will be understoodthat the evaporation time of the fuel particle sprayed into thecombustion element becomes longer and the interior thereof is contactedmore hardly by air, as the size of said fuel particle (hereinafterreferred to as sprayed particle size) becomes larger. A larger sprayedparticle size facilitates the occurrence of excess fuel regions in thecombustion chamber and is a cause of smoke generation. The sprayedparticle size is influenced by the fuel atomizing characteristic of thefuel injection nozzle.

Fuel injection nozzles are classified broadly into two types in terms ofspray method. Namely, one is a type of fuel injection nozzle whichsprays fuel with pressure (hereinafter referred to as pressure spraytype fuel nozzle) and the other one is a type of fuel injection nozzlewhich sprays fuel by making use of air pressure (hereinafter referred toas air spray type fuel nozzle). In case of the air spray type fuelnozzle, the sprayed particle size is smaller than in case of thepressure spray type fuel nozzle. However, the air spray type fuel nozzlehas the serious disadvantage that it calls for a compressor solely forcompressing the air used for spraying fuel. Further, with the air sprayfuel nozzle, there must be provided, in addition to a fuel flow controlsystem, an air flow control system and an air piping which render theconstruction of the gas turbine complicated.

In gas turbines, the pressure spray type fuel nozzle is generally beingused at the present time, As one type of the pressure spray type fuelnozzle, there is known a spiral spray type fuel nozzle which sprays fuelparticles in the form of a spiral flow. This type of fuel nozzleincludes a fuel nozzle having dual nozzle openings consisting of a smallopening from which fuel is constantly sprayed and relativelylargeopenings which are not opened at the time of ignition (hereinafterreferred to as dual opening type spiral fuel nozzle). This duel openingspiral type fuel nozzle has the advantages that the time required fromthe start of a gas turbine to the rated speed can be shortened, and thatthe flow rate of fuel can be regulated simply by varying the spray pressure by means of a fuel pump. On the other hand, with the duel openingtype spiral fuel nozzle, the fuel particles are sprayed in a conicalshape and most of them are concentrated at the peripheral portion ofsaid conical shape, substantially no fuel particles being present in thecentral portion of the conical shape. Practically speaking, the numbersof fuel particles at the peripheral portion is about 27 times that offuel particle present in the central portion, with respect to the unitarea of the conical shape. Further, the mean sprayed particle size is aslarge as about 320 microns, and even larger and about 370 micronsespecially at the peripheral portion. Thus, it will be understood thatfuel particles of large diameters are present in a large number at theperipheral portion of the conical spray of fuel. In consideration of theair and fuel concentrations at this portion, it will be readilyunderstood that excess fuel regions occur locally in the combustionchamber, which are obviously the major cause of incomplete combustionand high smoke concentration. For eliminating the excess fuel regions,only increasing the primary air is insufficient and the fuel atomizingcharacteristic of the fuel nozzle needs to be improved. Such a tendencycan be said on all of pressure spray type fuel nozzles.

SUMMARY OF THE INVENTION The primary object of the present invention isto provide a novel pressure spray type fuel nozzle which overcomes thedisadvantages of the conventional ones and is capable of reducing thesprayed fuel particles.

Another object of the invention is provide a pressure spray type fuelnozzle which suppresses the generation of smoke even when used with acombustion element of gas turbine.

Still another object of the invention is to provide a pressure spraytype fuel nozzle which enables even a less volatile oil, such as heavyoil, used as fuel to be burned satisfactorily.

Still another object of the invention is to provide a pressure spraytype fuel nozzle which is capable of dividing into smaller particles thecoarse fuel particles concentrating to the outer peripheral portion of aconical spray of fuel injected from the nozzle opening and enables auniform distribution of fuel particles to be obtained.

A further object of the invention is to provide a pressure. spray typefuel nozzle which divides the sprayed fuelparticles by making use ofpart of the combustion air being supplied into a combustion chamber and,therefore, is very simple in construction and inexpensive, withoutrequiring an additional air supply source.

The present invention is characterized in that air discharge openingsare provided around the opening of a fuel injection nozzle connected toone end of a fuel passage facing the combustion chamber of a combustionelement, and each of said air discharge opening is of such constructionthat air discharged therefrom forms a spiral air flow which contactsfrom the outside the outer periphery of a conical spray of fuelparticles injected into the combustion chamber from the fuel injectionnozzle. Therefore, with the fuel injection nozzle of the invention, theouter peripheral portion of the conical spray is disturbed by the spiralair flows. with the result that the coarse fuel particles concentratingto said portion are divided into smaller particles and disperseduniformly in the combustion chamber, providing for satisfactorycombustion of fuel. Further, the spiral air flows are formed by makinguse of part of the combustion air supplied into the combustion chamberand hence, a special air supply source is not required. This isadvantageous in rendering the fuel injection nozzle of the inventionvery simple in construction and inexpensive.

The objects, set forth above, other objects and the unique features ofthe present invention will be more fully understood from the followingdetailed description when taken in conjunction with the accompanyingdrawings. It should be understood, however, that the drawings are onlyillustrative and not limitative to the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a vertical sectional view ofan embodiment of the pressure spray type fuel injection nozzle accordingto the present invention;

FIG. 2 is a front elevational view showing in detail the air dischargeopening unit shown in FIG. 1;

FIG. 3 is a fragmentary view of the air discharge opening unit, lookingin the direction of the arrow III in FIG. 2;

FIG. 4 is a sectional view illustrating diagrammatically spiral airflows and fuel particle flow, formed by the nozzle of the invention,relative to the axis of the nozzle opening;

FIG. 5 is a characteristic graph showing the flow rate distributions ofsprayed fuel, of a conventional dual opening type spiral fuel nozzle andthe pressure spray type fuel nozzle of the invention;

FIG. 6 is a characteristic chart showing the particle size distributionsin the radial direction of fuel particles sprayed by the conventionaldual opening type spiral fuel nozzle and the pressure spray type fuelnozzle of the invention; and

FIG. 7 is a vertical sectional view of another embodiment of the fuelnozzle according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there isshown an embodiment of the pressure spray type fuel nozzle according tothe invention generally indicated by numeral 11, as mounted in acombustion element (hereinafter thr pressure spray type fuel nozzle ofthe invention will be referred to simply as fuel nozzle, to distinguishit from conventional pressure spray type fuel nozzles). The fuel nozzlel l comprises a nozzle body 12 having a fuel passage (not shown) formedtherein and a fuel discharge opening 27 provided at the forward end ofsaid fuel passage, a cap l4 surrounding said nozzle body 12 to form anannular air passage 23 therebetween, a spiral passage unit 18 providedat the forward end of the air passage 23 defined by said nozzle body 12and cap 14 and having air discharge openings 20, and a supporting member21. The fuel discharge opening 27 is located on the axis 29 of thenozzle body 12 and is of the ordinary one capable of spraying fuel in aconical shape coaxial with the axis 29. The nozzle body 12 is connectedto the supporting member 21 by the ordinary means, e.g., screws. Theforward end of the cap 14 is so shaped as to define an air dischargeopenings 20 between the inner surface thereof and the outer surface ofthe spiral passage unit 18. The cap 14 is connected to the supportingmember 21 through screw engagement between external threads formed onthe outer surface of the rear end portion of said cap 14 and internalthreads formed on the inner surface of the forward end of saidsupporting member 21. The spiral passage unit 18 is secured between thenozzle body 12 and the cap 14 at the same time when the cap 14 isconnected to the supporting member 21. The spiral passage unit 18 mayalternatively be connected to the nozzle body 12 by means of screws. Thespiral passage unit 18, as shown in FIG. 2, has a plurality of groovesformed in the conical outer surface thereof which form air dischargeopenings 20 together with the inner surface of the cap 14. Each of theair discharge openings 20 has an angle a of inclination to the axis 29of the nozzle body 12 as shown in FIG. 1, and an angle 6 of torsion tothe axis 29 as shown in FIG. 3. The upper and lower surfaces of the airdischarge opening are parallel to the air flowing direction, but notnecessarily and one of them may be inclined relative to the other sothat said air discharge opening may be progressively reduced in crosssection toward the downstream of the fuel nozzle 11. The air dischargeopenings 20 and the fuel discharge opening 27 do not have a commonpassage at any point within the fuel nozzle llll.

An outer cylinder, generally indicated by numeral 35, of the combustionelement is composed of a cylinder 36 and an end plate 37 perpendicularto said cylinder 36. The supporting member 21 supporting the fuel nozzleH is fixed to the end plate 37 by means of bolts. In the outer cylinderis disposed a liner 39 which de fines a combustion chamber therein andis provided with primary air inlet openings 41, secondary air inletopenings (not shown) and slit-like louvers 43. The outer cylinder 35 andthe liner 39 form therebetween a passage 26 for combustion air Sll. Oneend of the liner 39 is closed and the forward end of the fuel nozzle 11is projecting into the combustion chamber 43, with the cap 14 located atthe center of said closed end of the inner 39, to spray fuel into saidcombustion chamber. The other end of the liner 39 is open fordischarging the combustion gas. The cap 14 has a number of apertures 16formed through that portion thereof which is exposed in the passage 26.The air discharge openings 20 are communicated with the passage 26through the passage 23 and the apertures 16. The total cross.

sectional area of the air discharge openings 20 is made smaller than thecross sectional area of the passage 23 and the total cross sectionalarea of the apertures 16. Between the nozzle body 12 and the spiralpassage unit 18 is formed an annular passage 25 which is incommunication with the passage 23'and open at the forward end fordischarging air along the forward end face of the nozzle body 12.

The coarse fuel particle dividing effect of the present invention isachieved by spiral flows of air discharged from the air dischargeopenings 20 which contact from the outside the outer periphery of theconical spray of atomized fuel particles injected from the fueldischarge opening 27, where the coarse fuel particles are present in alarge number. Namely, the coarse fuel particles are divided into smallerparticles by taking advantage of the velocity energy of the spiral airflows. This principle will be described hereunder with reference to FIG.4.

FIG. 4 is a sectional view diagrammatically showing in side elevationthe conical spray 57 of fuel particles injected from the fuel dischargeopening 27 and the spiral flows of air discharged from the air dischargeopenings 20, relative to the axis 29 of the fuel nozzle. The centers ofthe air discharge openings 20 are located on a circle concentric withthe axis 29 of the fuel nozzle, which is a distance r spaced axiallyfrom the fuel discharge opening 27 and has a radius a (hereinafter alldistances from the air discharge openings 20 are with reference to thiscircle). At a point a distance h spaced axially downstream from the airdischarge openings 20, the coarse fuel particles discharged from thefuel discharge opening 27 at an angle 2 of injection and being presentat the outer peripheral portion of the conical spray 57 of fuelparticles, are spaced radially from the axis 29 of the fuel dischargeopening by a distance R which is represented by the following formula:

R, (h r) ma Here, it should be understood that in FIG. 4 axial distancesmeasured downstream from the fuel discharge opening 27 are regarded asand radial distances measured upwardly from the axis 29 of the fuelnozzle are regarded as At the point the distance 11 spaced axiallydownstream from the air discharge openings 20, the spiral flows 55 ofair discharged from said air discharge openings pass the points spacedradially from the axis 29 of the fuel nozzle by a distance R, which isrepresented by the following formula:

R i (htan6) (a htanbz) 2 wherein a is the angle of inclination of theair discharge openings to the axis of the fuel nozzle, and

6 is the angle of torsion of the air discharge openings to the axis ofthe fuel nozzle.

The spiral air flows 55 contact the outer periphery of the conical spray57 of fuel particles at the point the distance h spaced axiallydownstream from the air discharge openings 20, when equations (3) givenbelow are satisfied:

R R (dR /dh) (dR /dh) 3 In the event when the axial position of the airdischarge openings 20 are changed with respect to the fuel dischargeopening 27, the radius a from the axis 29 of the fuel nozzle is adjustedsuch that the spiral air flows will not interfere with the conical spray57 of fuel particles sprayed from the fuel discharge opening 27.

On the contrary, the positions of contact between the spiral air flows55 and the outer periphery of the conical spray 57 of fuel particles canbe optionally changed by selectively changing the angle: a ofinclination and angle 6 torsion of the air discharge openings 20 to thefuel discharge opening 27 which. has a specific spray angle.

In formulae (1) and (2), the angle a of inclination and the angle 6 oftorsion which satisfy equation (3) are subjected to certain limitationsin respect of the selectable ranges thereof, for the following reason:namely, when the angle a of inclination is extremely large or the angle6 of torsion is extremely small, the spray angle of the fuel particles57 becomes undesirably small, with the result that the fuel particlesconcentrate to the axis 29 of the fuel nozzle and the finely atomizedfuel particles join again, forming particles of large diameters.Conversely, when the angle a of inclination is extremely small, thepoints of contact between the spiral air flows 55 and the conical spray57 of the fuel particles move away axially downstream from the airdischarge openings 20, so that the velocity energy possessed by thespiral air flows 55 cannot be used effectively for the division of fuelparticles into smaller particles. Further, when the angle 6 of torsionis extremely large, the spiral air flows 55 do not contact the conicalspray 57 of fuel particles.

With the spray angle of the fuel discharge opening 27 being 80, asatisfactory result can be obtained when the angle a of inclination ofthe air discharge openings 20 is in the range of 30 and the angle 6 oftorsion thereof in the range of 15 50, and the best result can beobtained when the angle a of inclination is 45 and the angle of torsionis 25. Using a fuel nozzle having air discharge openings 20 of which a45 and 6 25, the flow rate distribution and particle size of sprayedfuel were measured at the point of contact between the spiral air flows55 and the conical spray 57 of fuel particles, namely at a point 140 mmspaced axially downstream from the air discharge openings 20, with theresults shown in FIGS. and 6.

FIG. 5 shows the radial distribution of the sprayed fuel particles. Itwill be seen that, with the fuel nozzle of the invention, the number offuel particles present in the vicinity of the nozzle axis is larger thanwith the conventional dual opening type spiral fuel nozzle, and that thenumber of fuel particles at the portion where the fuel particlesconcentrate most is only about eight times that at the nozzle axis, withrespect to unit area and thus the fuel particles are distributedconsiderably uniformly.

FIG. 6 shows the particle size distribution of fuel particles in theradial direction. It will be seen that, with the fuel nozzle of thisinvention, the mean particle size becomes as small as about 230 micronsand the particle size difference in the radial direction decreases.Thus, the fuel nozzle of the invention is advantageous in respect ofparticle size distribution as well as flow rate distribution of sprayedfuel.

The spiral air flows are formed by making use of part of the combustionair passing in the space between the liner 39 defining the combustionchamber and the outer cylinder 35 of the combustion element surroundingsaid liner 39, to be supplied into said combustion chamber. This part ofthe combustion air is injected into the combustion chamber from the airdischarge openings by virtue of a pressure difference between theinterior and exterior of the liner, to form the spiral air flows.Therefore, it is unnecessary to provide an additional compressor whichhas been required by the conventional air spray type fuel nozzle solelyfor spraying fuel. With the fuel'nozzle of the invention, theatomization of fuel into fine particles is possible, only with thecompressor provided for a gas turbine as a combustion air source.

The process in which the fuel is atomized by the fuel nozzle of theinvention will be described in greater detail hereunder with referenceto FIG. 1. The fuel nozzle of the invention is provided with the airdischarge openings 20 each having an angle a of inclination and an angle0 of torsion to the axis of the fuel discharge opening 27 from which thefuel injected in the form of a conical spray having a spray angle (b.Now, let it be supposed that the angle of inclination and the angle oftorsion to satisfy equations (1) and (2) are x and y respectively, i.e.,or x and 0 y, and the spray angle is 3, Le,

The combustion air 51 supplied from the compressor (not shown) of thegas turbine and passing in the passage 26 flows into the combustionchamber 45 from the primary air inlet openings 41, the secondary airinlet openings (not-shown) and the louvers 43 formed in the liner 39. Inthis case, part of the combustion air 51 flows into the passage 23 fromthe apertures 16 as the air 53 discharged into the combustion chamber 45from the air discharge openings 20 to form the spiral air flows 55 eachhaving the angle a of inclination, that is the angle x, and the angle 0of torsion, that is the angle y, to the axis 29 of the fuel dischargeopening 27. In the conical spray 57 of atomized fuel discharged from thefuel discharge opening 27, the number of fuel particles is small at theportion adjacent the axis 29 and is large at the outer peripheralportion of the conical spray, and the majority of the fuel particles atthe outer peripheral portion of the conical spray are large in particlesize. The spiral air flows 55 contact the outer periphery of the conicalspray 57 of fuel particles at points downstream of the fuel nozzle 11.The large fuel particles present at the outer peripheral portion of theconical spray 57 are further divided by the actions of these spiral airflows 55 into finer particles. The spiral air flows 55 also act todisperse uniformly the fuel particles concentrating to the outerperipheral portion of the conical spray 57. Thus, fine fuel particlesand uniform distribution of the fine fuel particles are obtaineddownstream of the contacts between the conical spray 57 of fuel and thespiral air flows 55, and excess fuel regions are reduced. It is also tobe noted that mixing of fuel and air is promoted by the spiral air flows55. By the action of the spiral air flows 55, the fuel particles arealso caused to make a spiral motion, so that the retention time of thefuel particles within the combustion chamber 45 is prolonged andaccordingly, the time in which the fuel particles receive heat from thecombustion gas formed in said combustion chamber 45 is prolonged,whereby the evaporation of the fuel particles is promoted. As a result,stable combustion is obtained within the combustion chamber 45 and thesmoke concentration in the exhaust gas is reduced to an invisibledegree.

Part of the air 53 passing in the passage 23 flows into the annularpassage 25 formed between the nozzle body 12 and the spiral passage unit18, at a point upstream of the air discharge openings 20, and dischargesalong the forward end face of said nozzle body 12 to prevent carbon fromattaching to said end face of the nozzle body 12.

In the embodiment described above, the apertures 16 for leading thecombustion air 51 into the passage 23 therethrough are formed in the cap14, it should be understood that these apertures 16 may alternatively beformed in the supporting member 21. In this case, as shown in FIG. 7,the supporting member is provided with a cap mounting portion 61projecting into the passage 26 through the end plate 37 of thecombustion element and a cap 14 is connected to said cap mountingportion 61. The apertures 16 are formed in the cap mounting portion 61at points upstream of the cap 14, for leading part of the combustion air51 therethrough into the passage 23. The same effect as has beendescribed above can also be obtained with such construction.

In order to impart the maximum velocity energy to the spiral air flows55 by taking advantage of the pressure difference between the interiorand exterior of the liner 39, it is necessary to locate the airdischarge openings 20 as close to the combustion chamber 45 as possibleand to make tht total cross sectional area thereof smaller than thetotal cross sectional area of the passage 23 and the apertures 16. Thetotal cross sectional area of the air discharge openings 20 ispreferably 1.0 1.5 percent of the total area of the primary air inletopenings 41, the secondary air inlet openings (not shown) and thelouvers 43 provided in the liner 39. A larger proportion of the areawill result in an instable state of combustion during the transitionperiod from the ignition tothe rated output operation phase of the gasturbine. Namely, since the temperature of the combustion air 51 is lowduring the transition period, supplying an excessively large amount ofair from the air discharge openings will promote cooling of the fuelparticles sprayed from the fuel discharge opening 27 and retard theevaporation of the fuel particles.

We claim:

1. A pressure spray type fuel nozzle comprising a fuel discharge openinglocated at one end of a fuel passage for injecting fuel into acombustion chamber therethrough to form a conical spray of fuelparticles, and an air discharge opening provided exteriorly of said fuelpassage and adapted to form a spiral air flow within said combustionchamber which contacts from the outside the outer periphery of saidconical spray of fuel particles,

in which there are provided a plurality of said air discharge openingswhich are arranged on a circle concentric with said fuel dischargeopening and each of which has an angle of inclination and an angle oftorsion to the axis of said fuel discharge opening,

in which with 2 representing the spray angle of fuel particlesdischarged from said fuel discharge opening, R, (h 2) tan (1representing the radial distance from the axis of said fuel dischargeopening of the fuel particles present at the outer periphery of saidconical spray at a point distance it spaced axially downstream from saidair discharge openings and R (htanfi) 2 (a htanor) representing theradial distance from the axis of said fuel discharge opening of saidspiral air flows at said point, wherein a and l are the radial distanceand axial distance of said air discharge openings from the axis of saidfuel discharge opening respectively, each of said air discharge openingshas an angle a of inclination and an angle 6 of torsion to the axis ofsaid fuel discharge opening which satisfy the conditions R. R2 n (d l Ll) ar)... when R, and R are both plus or minus values.

2. A pressure spray type fuel nozzle according to claim 1, in whichthere is provided means for leading to said air discharge opening partof the combustion air passing in a space formed between a liner definingsaid combustion chamber therein and an outer cylinder of a combustionelement surrounding said liner and being supplied into said combustionchamber.

3. A pressure spray fuel type nozzle according to claim 2, comprising anozzle body having said fuel discharge opening and connected to asupporting member, a cap connected to said supporting member in a mannerto surround said nozzle body other than the portion of said fueldischarge opening and to form an annular air passage between it and saidnozzle body and formed with apertures for leading said combustion airinto said air passage therethrough, and a plurality of said airdischarge openings provided at the forward end of said air passage.

4. A pressure spray fuel type nozzle according to claim 2, comprising anozzle body having said fuel discharge opening and connected to asupporting member, a cap connected to said supporting member in a mannerto surround said nozzle body other than the portion of said fueldischarge opening and to form an annular air passage between it and saidnozzle body, said supporting member being formed with apertures forleading the combustion air into said annular passage therethrough, and aplurality of said air discharge openings provided at the end of said airpassage closer to said fuel discharge opening.

5. A pressure spray type fuel nozzle according to claim 1, comprising anozzle body having said fuel discharge opening and connected to asupporting member, a cap connected to said supporting member in a mannerto surround said nozzle body other than the portion of said fueldischarge opening and to form an annular air passage between it and saidnozzle body and formed with apertures for leading said combustion airinto said air passage therethrough, and a plurality of said airdischarge openings provided at the forward end of said air passage.

6. A pressure spray type fuel nozzle according to claim 1, comprising anozzle body having said fuel discharge opening and connected to asupporting member, a cap connected to said supporting member in a mannerto surround said nozzle body other than the portion of said fueldischarge opening and to form an annular air passage between it and saidnozzle body, said supporting member being formed with apertures forleading the combustion air into said annular passage therethrough, and aplurality of said air discharge openings provided at the end of said airpassage closer to said fuel discharge opening.

1. A pressure spray type fuel nozzle comprising a fuel discharge openinglocated at one end of a fuel passage for injecting fuel into acombustion chamber therethrough to form a conical spray of fuelparticles, and an air discharge opening provided exteriorly of said fuelpassage and adapted to form a spiral air flow within said combustionchamber which contacts from the outside the outer periphery of saidconical spray of fuel particles, in which there are provided a pluralityof said air discharge openings which are arranged on a circle concentricwith said fuel discharge opening and each of which has an angle ofinclination and an angle of torsion to the axis of said fuel dischargeopening, in which with 2 phi representing the spray angle of fuelparticles discharged from said fuel discharge opening, R1 + OR - (h - t)tan phi representing the radial distance from the axis of said fueldischarge opening of the fuel particles present at the outer peripheryof said conical spray at a point distance h spaced axially downstreamfrom said air discharge openings and R2 + OR - square root (htan theta )2 + (a htan Alpha )2 representing the radial distance from the axis ofsaid fuel discharge opening of said spiral air flows at said point,wherein a and t are the radial distance and axial distance of said airdischarge openings from the axis of said fuel discharge openingrespectively, each of said air discharge openings has an angle Alpha ofinclination and an angle theta of torsion to the axis of said fueldischarge opening which satisfy the conditions R1 R2 and (dR1/dh)(dR2/dh) when R1 and R2 are both plus or minus values.
 2. A pressurespray type fuel nozzle according to claim 1, in which there is providedmeans for leading to said air discharge opening part of the combustionair passing in a space formed between a liner defining said combustionchamber therein and an outer cylinder of a combustion elementsurrounding said liner and being supplied into said combustion chamber.3. A pressure spray fuel type nozzle according to claim 2, comprising anozzle body having said fuel discharge opening and connected to asupporting member, a cap connected to said supporting member in a mannerto surround said nozzle body other than the portion of said fueldischarge opening and to form an annular air passage between it and saidnozzle body and formed with apertures for leading said combustion aiRinto said air passage therethrough, and a plurality of said airdischarge openings provided at the forward end of said air passage.
 4. Apressure spray fuel type nozzle according to claim 2, comprising anozzle body having said fuel discharge opening and connected to asupporting member, a cap connected to said supporting member in a mannerto surround said nozzle body other than the portion of said fueldischarge opening and to form an annular air passage between it and saidnozzle body, said supporting member being formed with apertures forleading the combustion air into said annular passage therethrough, and aplurality of said air discharge openings provided at the end of said airpassage closer to said fuel discharge opening.
 5. A pressure spray typefuel nozzle according to claim 1, comprising a nozzle body having saidfuel discharge opening and connected to a supporting member, a capconnected to said supporting member in a manner to surround said nozzlebody other than the portion of said fuel discharge opening and to forman annular air passage between it and said nozzle body and formed withapertures for leading said combustion air into said air passagetherethrough, and a plurality of said air discharge openings provided atthe forward end of said air passage.
 6. A pressure spray type fuelnozzle according to claim 1, comprising a nozzle body having said fueldischarge opening and connected to a supporting member, a cap connectedto said supporting member in a manner to surround said nozzle body otherthan the portion of said fuel discharge opening and to form an annularair passage between it and said nozzle body, said supporting memberbeing formed with apertures for leading the combustion air into saidannular passage therethrough, and a plurality of said air dischargeopenings provided at the end of said air passage closer to said fueldischarge opening.